Effects of Inhomogeneous Ice Particle Habit Distribution on Passive Microwave Radiative Transfer Simulations

Accurately representing ice clouds in passive microwave radiative transfer models (RTMs) is considerably challenging as these clouds include numerous ice particles with complex shapes. Current RTMs often oversimplify this complexity by assuming spherical or singular nonspherical habits for these particles. This study improves the representation of ice clouds in RTMs, shifting from the oversimplified “one-shape-fits-all” approach to a more realistic approach describing the inhomogeneous distribution of ice habits. This improved representation is facilitated by the predicted particle properties (P3) microphysics parameterization scheme, which provides natural variability of the ice-phase hydrometeors’ microphysical properties. The impact of this improved representation on microwave scattering is evaluated by comparing the simulated brightness temperatures (TBs) with actual measurements from the global precipitation measurement (GPM) microwave imager (GMI) at scattering frequencies between 89 and 183 GHz, mainly focusing on tropical cyclone events in the Northwestern Pacific Ocean. The results show that the improved representation effectively describes the spatiotemporal variability of ice habits, improving the accuracy of TB simulations across the scattering channels. Moreover, investigations are conducted till the frequency of 664 GHz, emphasizing the potential importance of realistic ice habit distribution. Although some limitations exist, primarily relating to the model’s dependence on the P3 scheme and the limited range of the available ice habits, especially for rimed particles, this study takes a significant step toward improving the realism and accuracy of RTMs, providing a deeper understanding of ice clouds and their influence on RTMs.